'Just because a substance is legal, it doesn't mean it's safe.' Photograph: Alamy

A national film competition has been set up by campaigners raising awareness of the potentially devastating effects of club drugs and legal highs. The Why Not Find Out campaign by the newly launched Angelus Foundation will invite young people to make films about the best ways of getting naturally high, such as sports and music.

Judges will include Lord Puttnam and the winners will be guided by award-winning producers such as Simon Berthon who produced Wallis Simpson: The Secret Letters. The winning films will appear on TV.

The campaign is to be launched at the Tricycle Cinema in Kilburn, north London, on 14 November.

Maryon Stewart, who founded the Angelus Foundation in 2009 when her medical student daughter Hester, 21, died after taking the then legal GBL, said the legal status of a substance was no guarantee of safety.

Stewart, from Brighton, East Sussex, said: "Our children don't need to die or be harmed for life by these toxic chemicals falsely disguised as legal highs.

"It's natural for young people to want to have fun, but it's important that they stay safe and fully understand just because a substance is legal it doesn't mean it's safe."

Almost one-third of young people search for ways of getting legally high, according to a survey commissioned by the foundation. But two-thirds of the 16-to-24-year-olds surveyed admitted not being well informed about the risks linked with taking such substances. Side-effects of legal highs range from psychosis, depression, panic attacks, seizures, coma, loss of use of the bladder, and death, campaigners warned.

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